reinforce each other in all sorts of ingenious ways. The couplet, the ordinary quatrain, the Omar Khayyam quatrain, _terza rima_, the rondeau, the rondel, the triolet, and all the stanza forms, are simply different schemes of combining rhythm and rhyme, the two fundamental formative devices of all poetry. Like poetry, music welds its elements by means of two modes of arousing and fulfilling our expectations; but these, though they are somewhat analogous to poetic rhythm and rhyme, are so much less close to our ordinary experience that they will need a slightly more detailed explanation. All modern music is divided up into beats, or equal time divisions, arranged into groups or measures by some regular system of accentuation. The accented beats, like the accented syllables in verse, impress the mind as goals of movement, in reference to which the light beats are felt as transitions or preparations. The regularity of the alternation of transition and goal is such that the mind quickly forms the habit of expecting each goal beforehand, and of taking a proportionate satisfaction in it when it arrives. This process of expectation and fulfillment links the successive beats together in an organism, which we may call the musical foot, after its analogy with the poetic foot.[25] So limited is the mental span that it is practically impossible for us to group more than three beats together in this way into a single organism; and all music consequently consists of combinations of either duple feet (one light beat followed by a heavy), or triple feet (two lights followed by a heavy) or complex arrangements of both sorts together. After this fundamental grouping of the time-elements is made, the mind instantly proceeds to recombine the groups into larger groups called phrases or sections. This it does by the same device of accentuation, either actual or ideal. It conceives one measure or foot as heavier or more significant than another, and so leaves one as a transition, to approach another as a goal. Thus groups of simple elements become themselves the compound elements of a larger synthesis, and the entire musical fabric gains definiteness and organization through the process of aroused and fulfilled expectation. Any metrical formula, like that of a bugle call, interrupted at any note before the last, gives us as vivid a sense of incompleteness as a statue with arms and legs broken off, or a ruined building, or a mutilated picture.